Heat exchanger



Oct. 28, 1930. c. B. GRADY ,5

HEAT BXCHANGER Filed Jan. 24, 1927 5 Sheets-Sheet 1 17/ 19 1 INVENTOR.

(may: 2. ammr i. ATTORNEY.

Oct. 28, 1930. c. B. GRADY 1,779,538

HEAT EXCHANGER Filed Jan. 24, 1927 5 Sheets-Sheet 2 PM Z INVENTOR.

ATTORNEY.

0a. 2a, 1930. c. R-GRADY 1,779,538

HEAT EXCHANGER Filed Jan. 24, 1927 5 Sheets-Sheet 3 INVEN TOR C/ll/FM'J.25. GEM

0d. 28, 1930. c, DY 1,779,538

HEAT EXCHANGER Filed Jan. 24, 1927 5 Sheets-Sheet 4 F/ig: 4. INVENTOR.

M0725: 5. am

A TTORNE Y.

5 Sheets-Sheet 5 I N V EN TOR.

(Mill? 2?. 65/70) ATTORNEY.

C. B. GRADY HEAT EXCHANGER Filed Jan. 24, 1927 Oct. 28, 1930.

Patented Oct. 28, 1930 UNITED STATES PATENT OFFICE omnms B. GRADY, orwnsr omen, New JERSEY, ASSIGNOR 'ro 'mn'raoromcrm mrommme CORPORATION, Aconronazrron on NEW YORK HEAT nxcnaneaa This invention relates to heatexchangers and, more particularly to a method and ap paratus foreflectinma transfer of heat to both a gas, and liquid or vapor, from ahot fluid medium, usually gaseous; and has for its object the provisionof certain improvementswhereby these results can be accomplished in aunitary structure, with a high rate and efiicienc of heat transfer, lowresistance to the ow of gaseous media and natural circulation of theliquid to be heated.

In accordance with my invention, heat is extracted usuall from the wastegaseous products of com ustion and utilized for the purpose ofpreheating combustion air: and either to make steam, heat 'feedwater, ordis till oil, and for kindred uses more specifically referred tohereinafter.

' In general, the apparatus comprises a housin formed of boiler plate orsimilar materia provided with separate passa ewa s for the three mediapassing through 1t. preferred embodiment of my invention, hot waste asesof combustion enter the housin .throug a conduit in the upper portion anpass around boiler tubing arranged in a preliminary heat absorbing'chamber. a The tubing is preferably arranged vertically in order toprovide for natural circulation of the liquid or va or contained thereinand to revent the Formation of steam pockets. he hot gases first passtransversely of the hottest portion of the tubesand are then divided anddirected around and along the tubes through vertically arranged ductssurrounding one or a plurality of tubes. For operation with low andmedium temperature waste gas, metal ducts will be employed but ifrelatively high temperature waste gases are available from metallurgicalfurnaces or the like, I prefer to construct the ducts of material havinga high fusion temperature and high heat 'conductivity such ascarborundum or other refractory material capable of transmitting radiantheat. Although one such duct may surround an entire row or bank oftubes, I prefer to surround each tube with a duct of circular crosssection positioned concentrically with respect to the axis of the tube.The waste gases discharge from the ducts into a collect:

ing and final heat absorbing chamber where they again pass along andacross the tubes and are finally discharged from the apparatus through aconduit leading to the exhaust fan or stack. V

Air to be preheated for combustion purposes, or other gas to be heatedis forced or drawn through a conduit and into the apparatus immediatelyabove the lower or collecting chamber and passes transversel around theducts at least once and preferab y two or more times in order toincrease the temperature and to render the heating uniform.

In accordance with my method, the temperature of the liquid in the tubesmay be controlled by varying the velocity of the air or other gasflowing in contact with the walls of the ducts for example; if the airflow is increased the walls of the ducts will be cooled more ra idly andless heat will be transferred to the tubes. This control may beaccomplished manually or automatically by means of thermostats connectedin circuit with the fan motor control or dampers in the air conduits,and the liquid or vapor temperature thus maintained at any predetermineddegree.

For purposes of compactness and to increase the surface exposed to thehot gases, the liquid carrying tubes are preferably so arranged in rowsthat one header at the top and one at the bottom will accommodate tworows. The headers are positioned half-way between rows and the tubesbent inwardly and expanded into the headers along the center linesthereof. The lower headers are connected to a cross header intowhich theliquid to be heated is admittedand the upper headers likewise open intoa cross header for collecting the heated liquid or vapor.

The hot gases entering the apparatus come into contact with the hottestportion of the tubing at their highest temperature whereby advantage ofthis temperature may be taken either to make steam, increase steamtemperature, vaporize oil, or as an alterna; tive, to permit a rapidflow of a large volume of liquid to be preheated such as boilerfeedwater or oil passing to a still. The waste gases in passing alongthe tubes in the ducts above referred to are gradually cooled bytransferring a portion of their heat to the tubes and a portion to thewalls of the ducts around which the air to be preheated is passed, therelative quantities of heat transferred to ducts and tube walls beingdependent upon the respective areas of the walls of the ducts and tubes.By varying the areas of the duct with respect to the tubes thequantities of heat transferred to either medium can be varied to suitthe requirements of the installation. In order that an e'fiicienttrans-- fer of heat to the air and liquid can be effected, and toobtaindesired temperatures in both media, the air first passes around thelower, cooler portion of the ducts and is discharged from the hottestportion; the liquid first enters the coolest portionof the apparatus,the collecting and final heat adsorbing chamber, and it follows that inthe upper portion of the apparatus the liquid, air and waste gas will beat their highest temperatures, the heat transfer to liquid beingcounterflow and to the air substantially counterflow. In all cases thetransfer of heat is effected by direct conduction through thin walls andfor this reason the transfer of heat is substantially direct.

The heat exchanger is applicable for use as a combined air heater andeconomizer suitable for steam boilers, and particularly for boilershaving relatively little convection surface, and in this case the tubesurface exposed in the preliminary heat absorbing chamber will functionsimilarly to a boiler pass, feedwater may be heated in the tubing andthe preheated air used for combustion purposes. It may also be used as awaste heat boiler, hot gases of combustion being taken from a cementkiln, oil still, metallurgical furnace or the like and the preheated airbeing used for combustion purposes. If the apparatus is to be used as awaste heat boiler, the lower cross header will function as a collectingor mu'd drum and the upper cross header as the steam drum. Itsapplication to the distillation of oils is similar to its use as an airheater and economizer, and in this case the oil will be forced throughthe tube, the air used for combustion purposes in the still, or if thewaste gas temperature is sufiiciently high, distillation may takeplace-in the tube and the distillate taken from the upper cross header,or if desired, the apparatus may be used to reboil the oil, and controlthe temperature of the oil as heretofore stated.

These and other features of the invention will be more clearly apparentby reference to the following description and accompanying. drawings, inwhich:

Fig.1 is a vertical, longitudinal 'section of the heat exchanger, takenon line 1--1 of Fig. 3, I

the tubes and ducts.

Fig. 2 is a Vertical cross section on line 2-2 of Fig. 3,

Fig. 3 is a sectional plan taken on line 33 of Fig. 1,

Fig. 4 is a sectional plan of a modified form of the heat exchangertaken on line 44 of Fig. 6.

Fig. 5 is a vertical cross section taken on line 55 of Fig. 4, and aFig. 6 is a sectional plan taken on line 6-6 of Fig. 4.

Referring to the drawings, and particularly to Figs. 1, 2 and 3, theapparatus is seen to consist of ahousing 1, made of boiler plate orsimilar material, into which hot waste gases or other fluid media aredrawn or forced through-a conduit 2 into a preliminary heat absorbingchamber 3. In the preliminary heat absorbing chamber, the gases passtransversely of the tubes 4, which may be of boiler tubing, and are thendivided and passed into ducts 5. Ducts 5 may be made of metal andexpanded into the tube sheet.6 which forms the bot-tom wall of thepreliminary heat absorbing chamber. If high temperature gases areemployed, such as the waste gaseous products of certainv metallurgicalprocesses, the ducts may be made of refractory tubing of high heatconductivity and high fusion temperature such as carborundum. The gasesthen pass downwardly within the ducts around and along the tubes 4transferring a part of their heat to the walls of the ducts and tubes,the relative quantity of heat so transferred being governed by therelative area of the walls of The lower ends'of the ducts 5 are expandedinto tube sheet 7, which forms the upper wall of the collecting chamber8 in which the gases again pass around the lower ends of the tubes 4 andare finally discharged through the exhaust conduit 9 leading to theexhaust fan or stack.

lower ends of each two" rows of tubes are bent inwardly, as shown inFig. 2, and are expanded into headers 10, each header. being positionedhalf-way between the two rows connected to it.

The headers 10 are connected to the inlet or cross header 11 by means ofthe elbows 12. If space permits these headers may be extended andexpanded directly in the cross header 11.

In the preliminary heat absorbing chamber 3, the upper ends of the tubes4 are likewise bent and are expanded into headers 13 so arranged thattheir under surfaces are exposed within the preliminary heat absorbingchamber and set flush with the under header 15 by means of elbows 16,cross header 15 serving to collect the heated fluid or vapor.

Air, or other gas to be preheated, enters the apparatus through theconduit 17, usually under fan pressure, and passes transversely of thelower portionof the ducts 5 and under bafile 18, then into chamber 25which serves as a return bend to direct the air again around and pastthe ducts between bafiles 18 and 19 and into chamber 20, which alsoserves as a return bend to direct the air transversely of the hottestportion of the ducts and be tween the baffle 19 and the tube sheet 6;the air finally discharging from the apparatus through the exhaustconduit 21 leading to the furnace. The number of baflie's or otherdevices usedto direct the air in transverse passes is dependent upon thetemperature and volume of preheated air necessary to meet therequirements of the specific installations.

In Figs. 4, 5 and 6, I have shown a modified and more simpleconstruction in whlch the resistance to flow of the waste gases and airis somewhat decreased, but the effective area of heat absorbing surfaceis less than in the preferred form. In the modified form of theapparatus the ducts 22, which correspond to the ducts 5, are ofrectangular cross section and surround a plurality of the tubes 4, forinstance an entire row as in the embodiment shown. The liquid carryingtubes 4 are straight and each row is expanded into the lower header 10and upper header 13. Although I have shown but one horizontal baflie 23and one return bend or chamber 24, it is to be understood that two ormore may be used, or those shown may be omitted entirely, depending uponthe degreeof preheat desired. The operation of-the apparatus as eitheran air heater and economizer, waste heat boiler and air heater, oilheater and oil still and air heater will be apparent from the foregoingdescription, but it is to be understood that various media other .thanthose suggested may be circulated through it, and that waste heat maybeextracted from hot vapors with condensation taking place in the ducts.

It is also to be understood that various modified constructions may bemade within the scope of the invention as defined in the claims appendedhereto, such as for example changes in the relative location of thevarious conduits and ducts and the entrance and exit sides for thevarious media circulated through the apparatus.

I claim:

1. A heat exchanger for transferring heat from a hot fluid medium to aliquid and a gas comprising a housing, an inlet conduit for the hotmedium opening into a chamber in the housing, a plurality of ductsserving as passageways for the medium opening into the chamber and alsointo a second chamberfor collecting the medium, liquid carrying tubesarranged within the ducts, and means for causing the gas to flow incontact with the outer walls of the ducts and in a series of passes, ineach of which the gas flows transverse to the axes of the ducts in asuccession of passes in which the gas flows transverse to the axes ofthe ducts,,

2. A heat exchanger for transferring heat from a hot gas to a liquid anda gas com rising, a housing, a preliminary heat absor ing chamber in theupper portion of the housing, means for admitting the hot gas to thechamber, a plurality of ducts for dividing and directing the gasdownwardly into a collecting chamber below the aforesaid chamber, aplurality of liquid carrying tubes arranged vertically Within the ducts,the lower ends of the tubes being connected to headers connected to across header to which the liquid is admitted, the upper ends of thetubes terminating in headers connected to a cross header for collectingthe heated liquid or vapor, means for directmg the gas to be heatedtransversely of and in contact with the outer walls of the ductsadjacent to the lower ends thereof, means for returning and againdirecting the gas transversely of the outer walls of the ducts above thefirst named directing means, and means for discharging the gas from thehousing adjacent to the-upper ends of the .ducts.

3. A heat exchanger for transferring heat from a hot gas to a liquid anda gas comtween rows, and means for directingthe gas to be heated trarsversely of the outer walls of the ducts.

In testimony whereof, I afiix my signature.

GHARLES B. GRADY.

